The main component of many plastic products is PVC, which is often called PVC. PVC is a kind of resin material, which can be made into many different products, such as packaging film, PVC plastic board and so on. Let's learn about PVC.
PVC is one of the earliest industrialized resin varieties in the world. PVC is one of the five general synthetic plastics. It is the second largest plastic product in the world, accounting for 29% of the total consumption of synthetic resin in the world. Since 2004, the domestic production has surpassed that of polyethylene and polypropylene, which has jumped to the first place and developed rapidly.
PVC resin is a kind of white powder or particle with particle size of 60-250 μ m, apparent density of 0.40-0.60g/cm3, density of 1.35-1.45g/cm3, refractive index of 1.544 (20 ℃), water absorption of ≤ 0.5%. Insoluble in water, alcohol and gasoline, it can swell or dissolve in ether, ketone, chlorinated aliphatic hydrocarbon and aromatic hydrocarbon. Under normal temperature, it has strong acid resistance, can withstand hydrochloric acid of any concentration, sulfuric acid of less than 90%, nitric acid of 50% - 60% and caustic soda solution of less than 20%, and is stable for salts. It can burn on the flame, and it will be extinguished after leaving the flame. The dielectric insulation is good.
PVC resin is composed of primary particles (also known as regional structure) of 200-500nm, which aggregate into primary particles (also known as secondary particles) of 1-2 μ m, and then aggregate into resin particles of 50-250 μ m by primary particles. The crystallinity of PVC is about 5-10%, and the ordered structure usually exists in the center of the regional structure.
PVC resin is a non crystalline, polar polymer, thermoplastic. The glass transition temperature is 75-105 ℃ according to the molecular weight. Its softening temperature and melting temperature are relatively high, and the pure PVC resin can only be plasticized at 160-210 ℃, because of the polar bond between macromolecules, PVC shows a hard and brittle performance. Moreover, when the temperature reaches 120 ℃, the dehydrochlorination of PVC begins, which will lead to the thermal degradation of PVC. Therefore, it is necessary to add stabilizers, plasticizers and other additives in the processing, and then to produce various PVC products after modification.
PVC products can be divided into soft and hard products according to the content of plasticizer. Generally, 0-5 parts of plasticizer content are hard products, 5-25 parts are semi-hard products, and more than 25 parts are soft products.
PVC plastics can be used for extrusion, injection molding, calendering, molding and blow molding. However, kneading must be carried out first to make all kinds of additives and PVC resin mix evenly at 90-110 ℃. Compared with other general resins, the processing formula and process are relatively complex.
PVC plastics have good physical and mechanical properties, which can be used in the production of building materials, packaging materials, electronic materials, consumer goods, etc., and widely used in industry, agriculture, construction, transportation, electric power, telecommunications, packaging and other fields. PVC consumption in China is mainly divided into two parts. One is soft products, mainly including wires and cables, films for various purposes, floor covering materials, fabric coating, artificial leather, various hoses, gloves, toys, plastic shoes and some special paints and sealants. The second is hard products, mainly including all kinds of profiles, pipes, plates, hard plates, bottles and other hollow containers.
